Plan ahead and know what you want. If you take the time to look at different modern home plans, you will have a much better idea of what you can expect from your designer. Once you know what you want, you can find a professional that fits your style and demands.
The challenge for the designer today is to produce ecologically-sound buildings without compromising contemporary concepts of beauty. There are plenty of examples of excellence in sustainable design which is soundly built, well-fit for its purpose, and an aesthetic delight. Even small luxury home plans are increasingly ecology-conscious in their choice of materials for conservation of resources and self-sufficiency.
When you are searching for a designer, search for one that is local to the area where you want your home built. Typically, local designers will have a better knowledge of the region, the laws, and the other issues surrounding your new house building project.
Modern home plans don't have to be expensive, but you definitely have to think about your budget so that you can compare it to the designs that are available and the ideas that you already have about the house that you want.